MCQs On Hydrogen for NEET

Hydrogen

Question 1. One would expect a proton to have a very large

1. Charge
2. Ionization potential
3. Hydration energy
4. Radius.

Answer: 3. Hydration energy

Proton (H⁺) ion being very small in size would have very large hydration energy

Question 2. The ionization of hydrogen atoms would give rise to

1. Hydride ion
2. Hydronium ion
3. Proton
4. Hydroxyl ion.

Answer: 3. Proton

It gives rise to Proton, \(\mathrm{H}_{(g)} \rightarrow \underset{\text { Tritium }}{\mathrm{H}_{(a q)}^{+}}+e^{-}\)

Question 3. Tritium a radioactive isotope of hydrogen, emits which of the following particles?

1. Neutron(n)
2. Beta(β^–)
3. Alpha (α)
4. Gamma(γ)

Answer: 2. Beta(β^–)

Tritium is a beta particle emitting radioactive isotope of hydrogen.

⇒ \(\underset{\text { Tritium }}{{ }_1^3 \mathrm{H}} \longrightarrow{ }_2^3 \mathrm{He}+\underset{\beta-\text {-particle }}{-1}{ }^0 e+0\)

Question 4. Which one of the following pairs of substances on reaction will not evolve H₂ gas?

1. Copper and HCl (aqueous)
2. Iron and steam
3. Iron and H₂SO₄ (aqueous)
4. Sodium and ethyl alcohol

Answer: 1. Copper and HCl (aqueous)

Copper is a noble metal, as it lies below hydrogen in the electrochemical series. Therefore, it cannot displace hydrogen from dilute HCl. Iron and sodium lie above hydrogen in the electrochemical series, so they can liberate H₂ either from steam or H₂SO₄ solution.

⇒ \(\mathrm{C}_2 \mathrm{H}_5-\mathrm{OH}+\mathrm{Na} \rightarrow \mathrm{C}_2 \mathrm{H}_5-\mathrm{ONa}+1 / 2 \mathrm{H}_2\)

⇒ \(\mathrm{Fe}+\mathrm{H}_2 \mathrm{SO}_4 \rightarrow \mathrm{FeSO}_4+\mathrm{H}_2\)

⇒ \(3 \mathrm{Fe}+4 \mathrm{H}_2 \mathrm{O} \rightarrow \mathrm{Fe}_3 \mathrm{O}_4+4 \mathrm{H}_2\)

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Question 5. Water gas is produced by

1. Passing steam through a red-hot coke
2. Saturating hydrogen with moisture
3. Mixing oxygen and hydrogen in a ratio of 1: 2
4. Heating a mixture of CO₂ and CH₄ in petroleum refineries.

Answer: 1. Passing steam through a red-hot coke

⇒ \(\underset{\text { Steam }}{\mathrm{H}_2 \mathrm{O}}+\underset{\text { Red hot }}{\mathrm{C}} \longrightarrow \underbrace{\mathrm{H}_2+\mathrm{CO}}_{\text {Water gas }}\)

Question 6. Which of the following metals evolves hydrogen on reacting with cold dilute HNO₃?

1. Mg
2. Al
3. Fe
4. Cu

Answer: 1. Mg

Mg reacts with nitric acid to give Mg(NO₃)₂ and evolves H₂ gas \(\mathrm{Mg}+2 \mathrm{HNO}_3 \rightarrow \mathrm{Mg}\left(\mathrm{NO}_3\right)_2+\mathrm{H}_2\)

Question 7. Which of the following statements about hydrogen is incorrect?

1. Hydronium ion, H₃O⁺ exists freely in solution.
2. Dihydrogen does not act as a reducing agent.
3. Hydrogen has three isotopes of which tritium is the most common.
4. Hydrogen never acts as a cation in ionic salts.

Answer: 2. Dihydrogen does not act as a reducing agent. and 3. Hydrogen has three isotopes of which tritium is the most common.

⇒ \(\mathrm{CuO}+\mathrm{H}_2 \rightarrow \mathrm{Cu}+\mathrm{H}_2 \mathrm{O}\)

⇒ \(\mathrm{ZnO}+\mathrm{H}_2 \rightarrow \mathrm{Zn}+\mathrm{H}_2 \mathrm{O}\)

⇒ \(\mathrm{Fe}_3 \mathrm{O}_4+4 \mathrm{H}_2 \rightarrow 3 \mathrm{Fe}+4 \mathrm{H}_2 \mathrm{O}\)

Hydrogen has three isotopes of which protium is the most common and tritium is radioactive.

Question 8. Match List 1 with List 2.

Choose the correct answer from the options given below:

1. (1) -(D), (2) – (A), (3) – (B), (4) – (C)
2. (1) -(C), (2) – (A), (3) – (B), (4) – (D)
3. (1) -(A), (2) – (B), (3) – (D), (4) – (C)
4. (1) -(B), (2) – (C), (3) – (D), (4) – (A)

Answer: 1. (1) -(D), (2) – (A), (3) – (B), (4) – (C)

MgH₂ – Ionic hydride

GeH₄ – Electron Precise hydride

B₂H₆ – Electron-deficient hydride

HF – Eiectron rich hydride

Question 9. Which of the following is electron-deficient? 

1. (BH₃)₂
2. PH₃
3. (CH₃)₂
4. (SiH₃)₂

Answer: 1. (BH₃)₂

Boron hydrides are electron-def,cient compounds.

Question 10. The method used to remove the temporary hardness of water is

1. Synthetic resins method
2. Calgon’s method
3. Clark’s method
4. Ion-exchange method.

Answer: 3. Clark’s method

Clarks process is used to remove the temporary hardness of the water. In this method, quick lime is added. The bicarbonates present in temporary hard water react with lime water to form insoluble calcium and magnesium carbonates which can be easily filtered off.

⇒ \(\underset{\text{Quick lime}}{\mathrm{CaO}}+\mathrm{H}_2 \mathrm{O} \longrightarrow \underset{\text{Lime water}}{{\mathrm{Ca}{\mathrm{OH}}_2}}\)

⇒ \(\mathrm{Ca}\left(\mathrm{HCO}_3\right)_2+\mathrm{Ca}(\mathrm{OH})_2 \longrightarrow 2 \mathrm{CaCO}_3 \downarrow+2 \mathrm{H}_2 \mathrm{O}\)

⇒ \(\mathrm{Mg}\left(\mathrm{HCO}_3\right)_2+2 \mathrm{Ca}(\mathrm{OH})_2 \longrightarrow 2 \mathrm{CaCO}_3 \downarrow+\mathrm{Mg}(\mathrm{OH})_2 \downarrow+2 \mathrm{H}_2 \mathrm{O}\)

Question 11. The number of hydrogen-bonded water molecule(s) associated with CuSO₄. 5H₂O is

1. 3
2. 1
3. 2
4. 5

Answer: 2. 1

The ionic formulation of CuSO₄ · 5H₂O is [Cu(H₂O)₄]H₂O · SO₄, in which four H₂O molecules are coordinated to a central Cu²⁺ ion while the fifth H₂O molecule is hydrogen bonded to the sulfate group.

Question 12. Which of the following groups of ions makes the water hard?

1. Sodium and bicarbonate
2. Magnesium and chloride
3. Potassium and sulphate
4. Ammonium and chloride

Answer: 2. Magnesium and chloride

The hardness of water is due to the presence of bicarbonates, chlorides, and sulfates of Ca and Mg. Hence, hard water will consist of Mg²⁺ and Cl^– ions.

Question 13. At its melting point, ice is lighter than water because

1. H₂O molecules are more closely packed in a solid state
2. Ice crystals have a hollow hexagonal arrangement of H₂O molecules
3. On melting of ice, the H₂O molecules shrink in size
4. Ice forms mostly heavy water on first melting.

Answer: 2. Ice crystals have a hollow hexagonal arrangement of H₂O molecules

In ice crystals, water molecules are linked through H-bonds in a hollow hexagonal arrangement so, the volume is large and the density is less. In a liquid state, this hollow arrangement breaks into closer arrangements of molecules. Consequently, the density is increased in a liquid state.

Question 14. Match the following and identify the correct option.

1. 1-C; 2-A; 3-B; 4-A
2. 1-C; 2-B; 3-A; 4-D
3. 1-C; 2-D; 3-B; 4-A
4. 1-A; 2-C; 3-B; 4-D

Answer: 1. 1-C; 2-A; 3-B; 4-A

Question 15. The structure of H₂O₂ is

1. Spherical
2. Non-planar
3. Planar
4. Linear.

Answer: 2. Non-planar

Hydrogen peroxide has a non-planar structure

Question 16. The volume strength of 1.5 N H₂O₂ solution is

1. 8.8
2. 8.4
3. 4.8
4. 5.2

Answer: 2. 8.4

Normality (N) = 1.5

We know that the equivalent weight of H₂O₂ is 17 and the strength of H₂O₂= Normality x Equivalent weight

= 1.5 x 17 = 25.5

⇒ \(\underset{(2 \times 34=68 \mathrm{~g})}{2 \mathrm{H}_2 \mathrm{O}_2} \rightarrow 2 \mathrm{H}_2 \mathrm{O}+\underset{(22.4 \mathrm{~L})}{\mathrm{O}_2}\)

Since 68 grams of H₂O₂, produces 22.4 litres of oxygen at NTP therefore, 25.5 grams of H₂O₂, will produce = 22.4/68 x 25.5 = 8.4 litre of hydrogen

Thus, the volume strength of the given H₂O₂, solution is 8.4

Question 17. The O – O – H bond angle in H₂O₂ is

1. 106°
2. 109°28′
3. 120°
4. 97°

Answer: 4. 97°

The bond angle of O – O – H in H₂O₂, is 97°

Question 18. Hydrogen peroxide molecules are

1. Monoatomic and form X^2-₂ ions
2. Diatomic and form X^– ions
3. Diatomic and form X₂^– ions
4. Monoatomic and form X^– ions

Answer: 2. Diatomic and form X^– ions

H₂O₂ is diatomic and forms H⁺ + HO₂^– (X^–) (hydroperoxide ion).

Question 19. Which of the following is the true structure of H₂O₂?

Answer: 2

is the true structure of H₂O₂

Question 20. The reaction of H₂O₂ with H₂S is an example of a reaction.

1. Addition
2. Oxidation
3. Reduction
4. Acidic

Answer: 2. Oxidation

It is an example of an oxidation reaction.

⇒ \(\mathrm{H}_2 \mathrm{~S}+\mathrm{H}_2 \mathrm{O}_2 \rightarrow 2 \mathrm{H}_2 \mathrm{O}+\mathrm{S}\)

⇒ \(\mathrm{H}_2 \mathrm{O}_2\) oxidises \(\mathrm{H}_2 \mathrm{~S}\) into \(\mathrm{S}\).

Question 21. Which of the following statements is not correct?

1. Hydrogen is used to reduce heavy metal oxides to metals.
2. Heavy water is used to study the reaction mechanism.
3. Hydrogen is used to make saturated fats from oils.
4. The H-H bond dissociation enthalpy is lowest as compared to a single bond between two atoms of any element.
5. Hydrogen reduces oxides of metals that are more active than iron.

Choose the most appropriate answer from the options given below:

1. 4, 5 only
2. 1, 2, 3 only
3. 2, 3, 4, 5 only
4. 2, 4 only

Answer: 1. 4, 5 only

Statements 4 and 5 are incorrect.

The H-H bond dissociation enthalpy is the highest for a single bond between two atoms of any element. Hydrogen reduces oxides of metals that are less reactive than iron.

Question 22. Some statements about heavy water are given below,

1. Heavy water is used as a moderator in nuclear reactors.
2. Heavy water is more associated than ordinary water.
3. Heavy water is a more effective solvent than ordinary water.

Which of the above statements is correct?

1. (1) and (2)
2. (1), (2), and (3)
3. (2) and (3)
4. (1) and (3)

Answer: 1. (1) and (2)

Heavy water is used for slowing down the speed of neutrons in nuclear reactors, hence used as a moderator. The boiling point of heavy water is greater (37 4.42 K) than that of ordinary water (373 K), hence heat water is more associated. The Dielectric constant of ordinary water is greater than that of heavy water, hence ordinary water is a better solvent.